Centralized traffic control systems for railroads



Jan. 17, 1956 N. B. coLEY 2,731,548

CENTRALIZED TRAFFIC CONTROL SYSTEMS FOR RAILROADS Filed Aug. 3, 1951 2 Sheets-Sheet l -lil V EN N. B. COLEY Jan. 17, 1956 2 Sheets-Sheet 2 Filed Aug. 3, 1951 I I I I ImmmcQwmmQmmf I I I II l if I I I I I I I I 4I I INVENTOR. N. B. CO Ieg MMM,

ATTORNEY Hfs I E I USN ZQH United States Patent C CENTRALIZED TRAFFIC CONTRGL SYSTEMS i' VFOR'RAILROADS' Nelson B. Coley, Rochester, N. Y., assigner to Generai -Railway Signal Company, Rochester, N. Y.

This invention relates to centralized traic control systemsfor' railroads, and it more particularly pertains to a system `for checking 'that a route is set 'up as designated before the transmission ofa signal clearing code for governing entrance tothe Vroute vis' permitted.

"Although centralized tratiic control systems of the cod'e'communic'ation type are so Organized in general as 'to have all :safetycir'cuits in the field 'so that an erroneous code cannot create a dangerous condition, an erroneous code can cause the establishment of a wrong route under'certain conditions-` lf'the'operator of the control machine `should not realize a wrong route had been set up, lthere could be considerable costly 'delay in train operation before 4the error would be corrected.

Generallyspealiin'g, andvv'ithout attempting to detine the scope'of the present invention, the' present invention prevents the setting up or a wrong route by permitting the transmission of a signal clearing code from the control oiiice'only after the track switches have been properlypositioned in correspondence with the switch control levers for such track switches at the control ofr'ice for aiie'ntireV route emanating from the signal desired to be cleared.` This is accomplished by the knocking down of a magnetic stick normal or reverse switch 'indication relay whenever it is designated that the associated track switch isrto be operated to its opposite position'. vrihe picking up of the magnetic stick Vrelay for the new position( that has' been selected in response to an indication transmittedfrom the fieldv station is required in order toiclois'eacircuit portion for a code determining relay associated with the Vtransmission of a signal clearing code to permit the transmission of such a code.

Another Yfeature of the system provided by the present invention is that for initiation of the code communication system-it is only necessary to actuate the respective switch and signal control levers for designation of the desired new positions, without requiring the actuation of a start button, toinitiate the code communication system from its'state of rest into operation for the transmission of the new'rontrol that has been designated. This starting means is'eiiect'ed by use of polarized circuits for' the control of normally energized start relays.

An object of the present invention is therefore to provide an Vimproved system of code communication involving the checking by indications received from the field of the positioning of track 'switches for a route before the transmission of a signal control governing entrance to the route is permitted.

Another object of the present invention is to provide control oliice starts directly in response to the actuation of switch'and signal control designating means by polarity control of normally energized change relays,` without requiring theuse of conventional start push buttons or switches.

"ther objects, purposes and characteristic features of the present invention will be in part vobvious from the accompanying drawings, and in part pointed out as the description of the invention progresses'.

2,731,53 Fatented J an. 17, 1956 ICC ln describing the invention in detail, reference is made to' the accompanying drawings in which parts having similar features or 'functions are designated by similar letter reference characters, and in which:

Fig. 'l illustrates apparatus at the control ollice for the initiation'of the code communication' apparatus into different cycles of operation for the transmission of respective switch and signal controls; i

Fig. 2 illustrates a section of the control panel of a control machine at the control oice having 'a track diagram of the track layout for which this embodiment or" the present invention is provided; Y'

Fig. 3 illustrates apparatus at the field station effecting the control of respective track switches and signals of a typical track layout in accordance with control codes received from the control oliice, and apparatus for'the transmission of indications to the control ottico asv to the conditions of the respective track switches at the eld station.

Conventional schematic diagrams have been DSCd vfor the disclosure of the system organization in the drawings, such drawings being preparedmore particularly to'faciiitate ari understanding of vthe rnode of operation of the system, rather than to attempt to point out the detailed construction and specilic arrangement of components that may be provided by those skilled in the art irraccordance with the requirements of practice. The symbols and (-)have been used to indicate' connections to the respective positive and negative terminals ofsuitabl batteries orother sources of direct current, and the symbols (B+) and (BF) have been used to Vindicate connections to the respective positive and negative terminals of a suitable split battery, or other source of direct current, having a center tap designated as (CN).

Although it is to be understood that the present invention is readily adaptable for the communication of switch and signal controls from a controloflice to a remote eld station for a track layout having a relatively large number of track switches and signals to be controlled, for the purpose of simplification o f this embodiment of the present invention, it has been considered suliicient for an understanding of the present invention that it be applied to lthe relatively simple trackl layout illustrated in Fig. 3, and shown in Fig. 2 as being constructed'as a diagram on the panel of the control machine at the control oliice. This track layout can be considered asV a small'part of a large track layout of an interlocking plant wherein three parallel tracks are interconnected by cross# overs ITS and STS. The track layout is divided into detector Vtrack sections in the usual manner, and signals 2R, 4R, and 6R are provided for governing eastbound traliic through the track layout While the signals 2L,'4L, and 6l. are provided for governing westbound traic through the track layout. The type of signals employed can be of any conventional type such as searchlight, position light, color light signals having individual color lamp units, or semaphore signals. The operation'of lthe track switches of the respective Crossovers TS and STS is by power switch machines at the respective ends of the Crossovers, the switch machines LASM and iBSM being associated with the operation of the track switches at the respective ends of the crossover TS, while' the switch layout constructed thereon and having manually operable switch and signal positions designating means SML' and SGL respectively, on the control panel either below the track diagram, or disposed along the track diagram, in accordance with the requirements of practice, as a means by which an operator of the control machine Vmay designate the respective routes to be set up through the track layout. It is to be understood that suitable indicator lamps such as the typical switch correspondence lamps ICK and SCK, together with other indicator lamps (not shown), are provided on the control panel for the purpose of keeping the operator informed as to the Yconditions of the apparatus at the eld station. The levers 18ML and 38ML are two position levers provided for the designation of the respective normal and reverse positions of the respective Crossovers TS and STS, and similarly three position signal control levers ZSGL, 4SGL, and 6SGL are provided in accordance with the usual practice for the Vmanual designation of the clear or stop indication desired to be displayed by the associated signals for both directions of traiic.

A normally energized change relay CH is associated with each of the switch and signal control levers SML and SGL as a start relay to be dropped away in response to the movement of its associated lever for initiating the system Vinto a cycleof operation for the Vcommunication of the vdesignated switchV or signal control. These relays are actuated by reversal of polarity upon the movement of the associated switch or signal control lever to a different position. Y

Relays LC are provided in association with the respective change relays CH, one relay LC being provided for each change relay CH. The purpose of these relays LC is to determine the code transmitted during any one cycle of operation of the code communication system, and Vtheir pickup circuits areV so organized that only one of theseV relays can be picked up at a time. Each relay LC when picked up is maintained energized for the duration of a control cycle-of operation of the code communication system by a stick circuit including the winding of a relay LCS which when picked up prevents the energization of another relay LC until the termination of the cycle of operation of the communicationY system that has been initiated.

Inasmuch as the present invention is applicable to vdifferentrtypes of code communication systems known in the art, it isv considered unnecessary for an understanding of the present invention to disclose the specific code comrnunication apparatus. The code communication apparatus can be provided, for example, as disclosed Vin the prior application of Coley and Albrighton, Ser. No.

207,253, led January 23, 1951, as disclosed in my application, Ser. No. 240,086, tiled of even date with the present application, which has resulted in U. S. Patent No. 2,626,314, dated January 20, 1953, or as disclosed inthe Hailes et al. patent, No. 2,399,734,7dated May 7, 1946.

v This embodiment of'the present invention has been particularly adapted for use with the code communication system Vas disclosed in myl application, Ser. No. 240,086, Ytiled of even date with the present application, whichV has resulted in U. S. Patent No. 2,626,314, datedlanuary 20, 1953.' Thus the relay contacts of relays identified by letter reference characters but with no circuits shown for the windings of Vthe relays are to'be considered as contacts of relays bearing similar referencecharacters in myV above v mentioned co-pending application, it being considered unnecessary to show the circuits for these relays in this case for anunderstanding of the present invention. Thus the contacts of relays L, CS, CSP, CP, CPP, C, 1V, 2V,

3V, 4V, and of a code oscillator CT are of relays having their operations and control circuits specically described in my above mentioned co-pending application.

Relays 1V, 2V, 3V and 4V are stepping relays that are operated successively and are used in setting up the se- Y quence of communication ofnthe respective code'charac= ters.

Relay L is a line relay at the control ofiice that is normally energized by a line circuit (not shown) extending from the control olce to the eld station as indicated by the dotted line shown in the drawings connecting the code communication apparatus at the respective stations.

Relays CS and CSP are respectively normally energized and normally deenergized relays that are used in the initiation of a cycle of operation of the communication apparatus. Relay CSP is a back contact repeater of relay CS.

Relays CP and CPP are provided at the control o'ce Vfor causing the complete repeat of the stepping for an indication cycle, thus providing that there are 14 steps in an indicationcycie as compared to 7 steps in a control cycle. These relays remain deenergized during a control cycle.l

For the reception of controls at the iield station, switch r and signal application relays are used according to the usual practice, the magnetic` stick relays lWZ and SWZ being provided for governing the power operation of the track switches of the crossovers 1 and 3 respectively, andV signal control relays ZRGZ and ZLGZ, 4RGZ and 4LGZ, and RGZ and 6LGZ being provided for governing the signals 2, 4, and 6 respectively for both directions of trail-ic. These relays are all adapted in accordance WithV the usual practice to be positioned by momentary energization as an output of the code communication system ceptedV by a train, if stick signalling is provided as is assumed for this embodiment of the present invention.

Apparatus for the communication of indications from the field station to the control office is provided according to the usual practice, such apparatus including change relays CH at the field station for the initiation of the respective indication cycles of operation of the communication system, and circuit selections including code determining relays LC, governing the indication characters as selected marks or spaces for transmission. i

Switch indication magnetic stick relays NWK, IRWK, 3NWK, and SRWK are provided at the control oilice in accordance with the usual practice for governing the encrgization of indicator lamps and the control'panel 20 of the control machine. In addition to these relays being adapted for normal indicationV purposes, they have a second winding which is used for checkingpurposes as a part of the present invention in a mannertoV be more readily understood'as the description progresses when reference is made to the mode of operation under specific assumed operating conditions. Y

Other relays including the track relays TR, track repeater relays TP, stop control relays B, and switch correspondence relays NCR and RCR are provided according to usual practice, and the control and Vfunctions of these relays are so Well known in the art that it is considered unnecessary to give vspecific consideration as to this part of the system.

Having thus considered the organization in'general of the apparatus of a specific embodiment Vor the present invention, a more detailed consideration willtnow be given as to the circuit organization upon considering certain typical modes of operation of the system.

Operation Like most system organizations of this nature, the system is normally at rest in that it is inactive for the communication of control or Vindication codes until there is a t 'and it is these normal conditions'that have been assumed in the drawings in indicating the positions ofthe respective relays, it also being assumed that the track switches have last been operated 'totheirinormal-p'ositiousj'laridtliat of the signals are at stop, 'andf-that'heftracke'layoiit fis unoccupied.' 'l

At this time, the change relays CH at the control ofice are'all'in their picked up positions and are'niintain'ed energized by stickcircuitscornparable to the'stic'k-circuit for the relay ICH, extending from ('-l-j, `in'cludingroiit contact 21 of relay ICH, contact 22 of leverv ISML- in bits left-hand position; and upper winding Aofj relay ICH;

`vThe -normal switch indication relays INWK and SNWK are shown as being picked'up under'conditions that are assumed as normal to correspond with ythe assumed normal positions'of their associated track switches.vv Y 'Y At the iield station the magnetic Stick switch control relays IWZ and SWZ (see Fig.:3) are illustrated as' being in their picked up positions because it is assumed that the last control communicated from the controloice has been forthe-power operationfof the track switches-of crossovers ITS- and STS -to their normal positions. `rlhus the correspondencerelays-INCR and SNCR areA also energized to normal conditions to repeat the normal positions of the associated switches.v

The lield changey relay CH is normally maintained picked up by la stick circuit provided according to usual practice so as to be interrupted when it is desired to initiate an indication cycle of operation of the code communication system in accordance with a change in a device to be indicated'.` For the purpose ofV an understanding of -the present invention, it has been considered unnecessary to illustrate-the communication of track occupancy indication and signal indications, and thus the portion of,V the stick circuit for the relayn CH including selections by contacts of these devices is merely indicated byXXv in the stick circuit. The organization of the stick circuit for the relay CH is such that the relay is maintained picked up under the-conditions assumed to be normal by energy feeding through back contact 23 of relay IRCR connected multiple with front contact 24 of relay IWZ, front contact 25 of relay INCR, front contact V2 6 of `relay QNCR, back contact 27 of relay SRCR connected` in multiple with front contact 28 of relay SWZ, and front contact 2 9 of relay CH.

To consider a typical example of the mode of operation upon the establishmentlof a route, it will be'assumed that, with the system in its normal condition as has been .d escribed',rit is desired to set up a route for the passage of an eastbound train from signal 2 over thecrossovers-fand 1 respectively to the'u'pper of the three'trc'ks as illustrated inthe track diagram on the control panel 2 0 (see'Fig. 2),. To designate the setting up of Ythis-route, the operator ot' the control 'machine actuates the switch control levers SSML andV 15ML to their respective reverse positions (right-hand operated positions), andY then operatesthe signal control lever ZSGL to its right-hand position for designating the clearing of signal 2 Yfor governingeastbound traic. The actuation of these switch and signal control levers can be in the order in which they have l:`eennamed,'orY all levers may be "actuated'at 'the' same time, it being desirable for obvious reasons that the switch positions be designated before'the designation of the signal to be cleared, or at least at the same time."A

y'if lit`is assumed that the' lever-shave Vall been actuated as ydescribed yat substantially the same time, threlays ICH, 3CH, and 2CH are all dropped away to initiate respective control cycles of operation of the code-communicationsystern for the communication of the desigriated switch and signal controls. The relay ICI-1 is dropped away because the shifting of the contact 22 of thelever I SML to its right-hand position energizes the lowerV winding of relay ICH and opens the circuit for the upper winding so that the ux is reversed in thatrelay, and thus the relay ICH becomes dropped away andropens its'owncircuit at'its front 'contact 21, whichreslts'firi tli'e shown z'and described inmy above 6 relay ICH having both of its windings deenergized. By aesimilar 'circnrfer'ganza'tioii the relays-'K219iL 'azCHi which-are yassociated Withth'e signal Y'coittrol lev'ez1'`-2SGI5,= ar'e"drpped'away'. The''relayZGl-I isvl dropediawayiby the energization'of its lower Winding through' ithe"'cbhtact 30:'o'f'the signal control lever ZSGLwhen this lever is actu atedfrornf'its center '(stop)-positiont'itsriglitlhand posi# tion.` "Itwtll be noted-'that asimilar energiza'tiohfoi'- relay 26H would be Yetec'tive if the-lever ZSGLWere'foperted to its left-hand position for designation of a signalto4V be clearcdicr Westboundtraic. -r i A function of the 'designation of a new switch control bythe actuation of aswitch-'c'ontrol lever isthe 'knockg ing downj'of the switcli'indcatiori r'elay"for'th"opposite switch position; if such switch: indicationrelay-is picked up-at-tha-t time. Thus, for example; upon actuationrof the switch control lever ISML"*toits-right-hand4 positoir, the relay EWK is knockeddown'bytlie energization'ofa circuit including contact' l52r`oflever-1SML iii-"its" right= handipesition, 4frorrt"contact-53 of relay INWK and lower windingofreiay-1NWKl VThe energizationof relay with' this polaritycauses the knockiugdown' ofthe relay; whichlopens-the circuit whichhas'j'ust lbeen energized at frontcontact 53. Y 4- Y i f i Similarly'when the lever 38ML is actuated to its righthand position, theccntact 5 4 Aof 'thatflevenwhen closed in its right-'hand position, applies energythrough -contact 545g of relay SNWK tothe lower winding of relay SNWK so as to cause the armature of that relay to be knocked down.

Having thus called for new positions for the track switches of both Crossovers ITS and @'IS, theout-ofcorrespondence lamps ICK and `SCK 'are respectively energized in accordance with the knocking down' of the normal switch indication relays as has been'describeclL Thus the lamp I CK, for example, becomes energized through back contact 5:6 of relay 'Il WYK, and back contact SI1-'ot relayIljIWK. Y 'f f it I naccordance with the relay ICH being dropped away, a circuit is closed to causethe picking tip of therelayILC extending-from (-1-), including back contact 31 of relay LCS, f ront'ontact 32 of relay C, back contact 3 3 oi relay I C-Ijl, 4lower winding of relay. ILC, and lback contacts 9 2 and- 93fo'ffrelays and 'INWK respectively, to (-5)'.

nvr b'rted that this circuit checksthar the aquarien of switclr control leverSML has' been effectiveto knock down relay INWK. 'lfhus'no switch controlcan relays .K- ndRWK are dropped away.

"Relayv ICH when picked up.is :maintained energized byfanstick circuit including the winding ofl 'relay LQSL; T hisrcircuit extends vfrom ('-l-JV, including backcontacts 34, 35', and 3 6 of relays CPB, QB, and CSR, respectively, front1 contacts 3 lv and 38 ofrelays C S, and L,- respectively, winding of relay LCS, front contact 39of relay ILC, and upp'rwinding'ofvrelay I LQto f(v Relay LC when pickedfup closes'aAV stick circuitv through its front contact 4t l to maintain the relays LCS and ILC picked up throughiitlthe'transmission of arcon'trol code. Energyis applied tothis stick 'circuit through any one of the steppingfrelay contacts -41,-l 4 2,v` l43, 'or4 44 Yof thel relays IV, 2y, Sty, and 4V, r'through the contact fingers and 46 ofthe oscilrtercr, 1 w

picking up oi the relay initiates the operationV of, the oscillatorMCT, which in t-urn causes-the stepping to be rendered `e1ective, andthe relay C is selectively energized hor deenergized during the respective steps to cause the 'transmission of vtheY selected code. 'The cnergization of the 'relay/ Cf is in accordance'witli the circuits selected through contacts' of the e'ly 1LC,"nlud,in`ig"fotcn tacts 4 7, 48, 'and 49 fof the respc ctliv"`stfeir` sfivn`a i well'kowttogthose familiar the" aitjand meriti pendingr 'application'. Y'Fach*time therelayi gladawatrentelasten-if ce ve transmitted until the corresponding switch indicationY arianne a mark by closing the line circuit through its front contact 50, and thus the selectiveopening and closing of the front contact 50 of relay C as the stepping progresses is effective to .cause the transmission of a selected switch control code to cause the operation of the track switches of the crossover 1TS to their .reverse positions in accordance with the designation of a reverse control code by the aci tuation of the switch control lever lSML to its right-hand position. Y

It is to be understood that the switchY control code transmitted from theV control oice to the iield station includes code charactersidentifying the station with which the switch is associated, or, in other words, for this embodiment of the present invention, a separate station is assumed for each of the Crossovers and for each pair of signals governing opposite directions of traic. Thus each o f the relays LC when picked up selects a distinctive station code for transmission, and renders the following charactersrof the code transmitted during that cycle as being selected by contacts (notrshown) Vof the switch or signal control lever that is associated with that relay LC.

Having thus described the mode of operation for the transmission of a selected switch control codeY to the iield station for the control of the track switches of crossover 1TS'to their reverse positions, it is to be understood that a similar mode of operation is eiective for the next cycle of operation for the transmission of aV switch control lcode for the power operation of the track switches ofV the crossover STS to their reverse positions in accordance with the lever SSML at the control oice being operated to its right-hand position. f

It will be obvious that the switch controls will be taken in the order that has been speciiiedin accordance with Vthe chain circuit organization for the energization of the relays LC, the closure of front contact 33 of the relay ICH being essential to permit the picking up of the relay SLC for the second control cycle. It will be noted that the relay ICH is picked up during the rst control cycle upon the energization of relay LCS by a circuit extending from including front contact 51 of relay LCS, front contact 19 of relay ILC, contact 22 of lever 18ML in its yright-hand position, and lower windingv of relay 1CH,

to The picking up of relay ICH closes front contact 21 to establish a stick circuit eiective to maintain the relay r1CH energized until the lever 18ML is actuated back to its normal position.

To consider'now what happens with respect to the ltransmission of the signal control that has been designated,

' it will be noted thatthe picking up of the relay SCH dur- Ving-transmission of the switch code for the` crossover-ST S closes the front contact 53 in the chain circuit for the energization ofrelays LC so as to permit the feeding of energy at the end of the control cycle'to the winding of the relay 2LC. The pickingup of the'relay 2LC, how ever, is made conditional, dependent upon the switch indication relays being positioned in accordance with an established route emanating from the signal that has been .designated to be cleared. "This is accomplished by a network'ofcircuit selections Yin the circuits for the respec- V tive relays LC that are associated with the communication 'of signal'controls which are so organized as to prevent the energization of any relay LC until a route is` establishedashas been described. Thus the knocking down of `the switch indication relays `INWK and SNWK upon designation of the Crossovers 1TS and STS to'be actuated to their reverse positions prevents the' energization of a relay-LC'vassociated with the transmission of a signal control until an indication is received 'from the ieldV that the switch controls that have been transmitted have been effective to cause the power operation.4 of the associated track 'switches totheir corresponding` positions. Thus, although the relay 2CH is assumed to be inits dropped ,away position,'the` relay 2LC cannot be picked up untilindications are received from the eld that the track switches have Vbeen operated in correspondence with the reverse positions that have been designated.

In accordance with the communication of the reverse control for the respective Crossovers TTS and STS, the

Y relays IWZ and SWZ (see Fig. 3) are respectively actuated to their dropped away positions, and thus the control circuits governed by these relays become energized with reverse polarity to effect the power operation of the switch machines SM.l Relay IWZ, for example, is eiective by the pole changing contacts 59 and 60 to cause the power operation of the track switches of the crossoverV lTS to their reversepositions. By a similar mode of operation, the contacts 61 and 62 vof relay SWZ pole change the circuit for the switch machines SM associated with the power operation of the track switches of the crossoverv STS so as to effect Vtheir operation to their reverse positions.

lt will be noted thatV the dropping away of the relay ltWZ- opens the circuit Vfor the normal correspondence relay INCR at front Contact 63, and thus causes this relay to become dropped away. The dropping away of the relay INCR, however, does not cause the start of an indication cycle at this time by the shifting of its contact 25 because' the back contact 24 of relay WZ has just been closed so as to maintain the relay CH energized during the crossover time of thecontact 25. Similarly, the closure of back contact 2S of relay SWZ just prior to the dropping away of the relay'NCR prevents Vtheopening of the stick cir.

cuit for relay CH upon the shifting of contact 26 of relay VSNCR.

When the track switches of the crossover VITS have been operated to their reverse positions and locked, the reverse biased polar correspondence relay TRCRV is picked up through back contact 63 of reiay WZ andpole changing contacts of the switch machine controlled mechanisms according to the usual practice. Similarly, when the track switches of the crossover STS are fully operated to their'reverse positions and locked, energy of reverse polarity is applied through the circuit controllers of the associated switch machines to the wires 64 and 65 so that the 1biased polar relay SRCR becomes picked up by energization through back contact 66 of relay SWZ.

The shifting of the Contact 2S upon the picking up of relay lRCRopens the stick circuit for the indication start relay CH because the frontcontact 24 of relay 1WZ is open at this time, and ,thus an indication cycle is initiated. Similarly an'indicationcycle can be initiated Vin accordance with the shifting ofthe contact 27 of relay VSRCR upon the picking up of that relay, because the lfront'contaet 2S of relay SWZ is open at that time. Thus an indication cycle is started,V and indications as to the positions of the respective switch correspondence relays NCR and RCR of the respective Crossovers are trans mittedv to the control oce. Y n

With the relayY RCR in its picked upposition during an indication cycle,.energy is applied through front contact 67 of relay fiCR, r'ront contact 68 of relay LC,

and wire 69 through the codeV communication system so as to apply energy to the wire 69a at the control office with a polarity toA cause the picking up of the magnetic stick relay IRWK. Similarly, with the relay SRCR (see Fig. 3) picked up,renergy is applied through front contact 7 of relay SRCR, front contact'71 of relay LC and lwire 72 to cause the energization through the code communication apparatus of the wire 72a (see Fig.v l) at'the control oiiicewith a polarity to cause the picking up vof the magnetic stick relay SRWK bythe energization of its upper winding. lt will be noted'that the pickingup of the relays IRWK and SRWK causes'the extinguishingl tions received frorn the tireldstation as has been described,

the circuit network for the energization of the relay 2LC is completed so that the signal control that is assumed to have been designated can now be transmitted. The relay ZLC, therefore, becomes picked up at this time by the energzation of a circuit extending from (-l-), including back contact 31 of relay LCS, front contact 32 of relay C, front contact 33 of relay lCH, front contact S of relay SCH, front Contact 74 of relay 6CH, front contact 75 or relay 4CH, back contact 76 of relay ZCH, lower winding of relay 2LC, contact 77 of the signal control lever ZSGL in its right-hand position, front contact 78 of relay SRWK, back contact 79 of relay SNWK, front contact 80 of relay IRWK, and back contact 81 of relay INWK, to

Thus the relay 2LC can be picked up, and the picking up of this relay establishes a stick circuit, including the winding of the relay LCS, and extending through the upper winding of relay ZLC and the stick contact S2 and the same circuit selections that have been described when considering specifically the stick circuit for the relay lLC. The picking up of relay LCS initiates the stepping and thus a signal control code is transmitted over the line circuit to the field station having characters selected in accordance with the control of the relay C through contacts of the relay ZLC and of the signal control lever 2SGL in accordance with the usual practice for the transmission of signal control codes. Each character of the code is a mark or a space (if the code communication system according to my above mentioned co-pending application is used) in accordance with whether or not the front contact of the relay C is closed during the respective steps of the communication cycle. It will be noted from the circuit that has been described for the energization of the relay ZLC that this circuit required a front contact to be closed of either the normal or reverse indication relay for each crossover that is included in the respective routes emanating from the signal 2R. If the route were set up with the track switches of the crossover STS in their normal positions, it would only be required that the relay SNWK be picked up to close front contact 83 because the crossover ITS would not be involved in such a route. if, however, the route to be established were through the track switches of the crossover STS in their reverse positions and one track switch or' crossover TS in its normal position, the circuit for the energization of the relay 2LC would necessarily require the closure of front contact 73 of relay SRWK and the front contact 84 of relay INWK. lt will therefore be readily apparent that by using a circuit network selected by contacts of the switch correspondence relays as has been described in the circuits for the relays LC for the respective signals, that it is arranged to automatically delay the transmission of a designated signal control until the prior designated switch controls have become eective to actuate the indication relays to positions in correspondence with the new positions to which the respective track switches have been operated.

The restoration at the end of the cycle of the relays LC which are provided for the transmission of signal controls, and the picking up of the associated relays CH, is comparable to the mode of operation that has been specifically described in accordance'with the transmission of switch controls for the operation of the relays ICH and lLC.

It will be noted that the circuit for energization of the upper windings of the switch indication relays NWK and RWK at the control oce check correspondence with the switch control levers for the associated track switches. That is, for example, the application of energy to the wire 69a by the code communication apparatus must energize the upper winding of relay IRWK through contact 90 of lever lSML in its right-hand position unless the relay IRWK is already picked up. In 'this case the switch lever contact 90 is shunted out of the control circuit for the upper winding of relay IRWK by front contact `9i so that relay IRWK can be knocked down by reverse polarity in its upper winding, irrespective of the position of the switch control lever SML. The circuit organization for the energization of the upper windings of the switch indication relays NWK and RWK is particularly to guard against the possibility of a switch indication relay being picked up to permit the transmission of a signal control under abnormal conditions where the transmission of an indication cycle from the ield is initiated without the track switch being operated in response to the switch control that has been designated.

Having thus described one speciiic embodiment of a route check system as applied to a relatively simple track layout it is desired to be understood that the system is readily adaptable for use with practically any track layout to be encountered in practice, and it is to be further understood that various adaptations, alterations, and modifications may be applied to the specic form shown in accordance with the requirements of practice within the scope of the present invention as defined by the appending claims.

What l claim is:

l. A centralized trailic control system for railroads for the control of a plurality of track switches and signals at a field station by code communication from a distant control oce comprising in combination, a normally-at-rest code communication system connecting the control olice and the field station and Veiective when initiated at the control otice to transmit selected control codes to the eld station and effective when initiated at the iield station to transmit selected indication codes to the control oce, manually operable switch control designation means at the control oliice for designating respective switch control codes for transmission to the lield station, said switch control designation means being eitective when actuated to initiate said code communication system, normal and reverse magnetic stick indication relays at the control office for the respective normal and reverse positions of the respective track switches, circuit means for energizing each or said magnetic stick relays with one polarity in response to the designation by said manually operable means of the opposite position of the associated track switch or with the opposite polarity in response to the communication by said code communication system of the corresponding position of the associated track switch, and manually operable designation means at the control oce for designating respective signal control codes for transmission to the field station, said signal designation means being effective when actuated to designate the clearing of a signal to initiate said code communication system, but not until one of said magnetic stick indication relays is actuated in correspondence with the full normal or full reverse position of its associated track switch for each track switch included in an available route emanating from the signal that has been designated.

2. A centralized tralic control system for railroads for the control of a plurality of track switches and signals at a lield station by code communication from a distant control oflice comprising in combination, manually operable switch designation means at the control ollce for selectively designating normal and reverse switch controls desired for the respective track switches, manually operable signal designation means at the control oiiice for selectively designating the clear and stop controls desired for the respective signals, a normally at rest code communication system effective when rendered active to communicate selected control codes from the control oiiice to the field station, or to communicate selected indication codes from the eld station to the control otiice, normal and reverse magnetic stick switch indication relays at the control ollice for the respective track switches, said switch indication relays being actuated in response to distinctive indication codes received from the iield station, initiation means at the control oice responsive to the actuation of said manually operable means for initiating said code communication system into a cycle of operation for the communication of switch or signal control codes in accordance with whether said manually operable signal designation means has been actuated, circuit means effective in response to the designation of a switch control for transmission for actuating to a predetermined position the switch indication relay for the opposite switch position, and check circuit means requiring said switch indication relays to be conditioned in correspondence with switch positions for an established route emanating from a signal having a signal clearing code designated for transmission before such designation can become elective to initiate said code communication system into a cycle of operation for the transmission of a signal clearing coded to the associated signal.

3. A centralized traic control system for railroads for the control of a plurality of track switches and signals at a field station by code communication from a distant control oiice comprising in combination, a normally at rest code communication system connecting the control otiice and the iield station effective when initiated at the control oilce to transmit selected switch or signal control codes to the iield station and eiective when initiated at the field station to transmit selected indication codes to the control oice, manually operable switch control designation means at the control otiice for designating respective switch control codes for transmission to the eld station, said switch designation means being effective when actuated to initiate said code communication system, normal and reverse magnetic stick indication relays at the control ofce for the respective normal and reverse positions of the respective track switches, circuit means for energizing each of said magnetic stick relays with one polarity in response to the designation by said manually operable switch designation means of the opposite position of the associated track switch, said circuit means being effective to energize each of said magnetic stick relays with the opposite polarity in response to the communication of an indication by said code communication system of the corresponding position of the associated track switch, manually operable signal designation means at the control oiiice for designating respective signal controls for each of the signals, a normally deenergized signal code determining relay effective when energized to initiate said code communication system for the transmission of a selected signal control code, and circuit means for energizing said signal control code determining relay for each signal when its associated signal is designated by said manually operable signal designation means as being controlled to a new position, said circuit means being eective only provided that there is one of said magnetic stick relays positioned in accordance with energization by said opposite polarity for each track switch in a route emanating from the signal having been designated.

4. A centralized traic control system for railroads for the control of a plurality of track switches and signals at a ield station remote from a control otlice comprising in combination, a normally at rest code communication system connecting the field station and the control oiice and elective when initiated at the control oice to communicate designated switch and signal control codes to the eld station, manually operable switch and signal control designation means at the control oflice operable respectively to a plurality of selected positions for eachY of the track switches and signals, a double-wound start relay at the control office for each track switch and for each signal, and circuit means for normally energizing one winding or the other of said start relay in accordance with the position of the associated manually operable means, said circuit means being effective upon the movement of the associated manually operable means to another position to shift energization of the associated start relay to the other winding with a change in the relative polarity, said circuit means being effective to normally maintain said 9 .La start relay energized through a front Contact of the associated relay, whereby each start relay is dropped away upon a change in the position of the associated manually operable means, and the dropping away of the startY relay opens its own circuit to remove energy from whichever winding has at last been energized.

5. A centralized traflic control system for the communication of controls for a signal from a control ofice to a'ield station comprising in combination, a manually operable three position selector device for the designation of the associated signals to be put to stop or cleared for one traic direction or the other, a double-Wound start relay at the control oice for the three position selector device, circuit means for governing the energization of one winding or the other of said start 'relayV selectively in accordance with the respective positions to which said device is actuated, said circuit means being effective to select the energization of the other winding of said start relay each time said three position device is actuated to a new position, and said circuit means being effective to energize each winding of said start relay always with the same polarity, but to oppositely polarize the two windings relatively, and said circuit means normally including a front contact of said start relay whereby the dropping away of that relay because of the reversal of polarity automatically opens the circuit for the last winding energized, and code communication apparatus including a line circuit connecting the control oice and the field station effective in response to the dropping away of said start relay to communicate a selected signal control code to the ield station in accordance with the position to which said manually operable three position device has been actuated.

6. A centralized traic control system for the communication of controls for a track switch from a control ofce to a field station comprising in combination, a manually operable multiple position selector at the control olce having respective normal and reverse positions for designation of respective normal and reverse switch controls to be communicated tothe eld station, a double wound start relay at the control oflice, circuit'means for governing the energization of one winding or'the lother of said start relay selectively Vin accordance with the respective normal or reverse position to which said multiple position selector is actuated, said circuit means being eiiective to energize each winding always with the same polarity, but to oppositely polarize the two windings relatively, and code communication apparatus including a line circuit connecting the control office and the field station effective in response to the Vdropping away of said start relay to communicate a selected switch control code to the field station in accordance with Vthe position to which said manually operable selector has been actuated.

7. A centralized tralic control system for the `communication of controls for a track switch from a control oiiice to a iield station comprising in combination, a manually operable multiple position selector device at the control oice having respective normal and reverse positions for designation of the respective normal and reverseV switch controls toV be communicated to the iield station, a double wound start relay at the control oice, circuit means for governing the energization of one winding or the other of said start relay selectively in accordance with the respective normal or reverse position to which said multiple position selector device is actuated, said circuit means being effective to energizeeach winding always with the same polarity, but to oppositely polarize the two windings relatively, said circuit means having energy normally fed for energization of the relay through a stick contact of said relay, and said circuit means having pickup energy momentarily applied after said start relay has initiated the transmission of a control code for ythe associated track switch, and code cornmunication apparatus including a line circuit connecting 13 the control office and the lield station effective in response to the dropping away of said start relay to communicate a selected switch cintrol code to the eld station in accordance with the position to which said manually operable means has been actuated.

8. A code communication system for the communication of selected controls for a multiple position device from a control oice to a eld station comprising in combination, a manually operable multiple position switch at the control oce for designating the respective positions to which said device is to be controlled, a double wound start relay at the control otlice, circuit means for governing the energization of one winding or the other of said start relay selectively in accordance with the respective position to which said multiple position switch is actuated, said circuit means being effective to energize each winding always with the same polarity, but to oppositely polarize the two windings relatively, said circuit means having energy normally applied to one or the other of the selected windings of the relay through a front contact of said relay, and said circuit means having pickup energy momentarily applied after said start relay has initiated the transmission of a control code for the associated device, and normally at rest code communication apparatus connecting the control ol'lice and the field station effective in response to the dropping away of said start relay to communicate a selected control code to the field station for the operation of said device in accordance with the position to which said manually operable switch has been actuated.

9. A centralized trac control system for the control of a plurality of track switches at a field station by code communication from a distant control oice comprising in combination, normally at rest code communication apparatus including a line circuit connecting the control ollice and the eld station and eiective when initiated at the control oflce to transmit selected control codes to the ield station and effective when initiated at the eid station to transmit selected indication codes to the control olice, manually operable switch control designation means at the control oice for designating respective switch control codes for transmission to the field station, normal and reverse magnetic-stick indication relays at the control oce for indicating the respective normal and reverse positions of the respective track switches, circuit means for energizing each of said magnetic-stick relays with one polarity in response to the designation by said manually operable means of the opposite position of the associated track switch and with the opposite polarity in response to the communication by said code communication system of an indication of the corresponding normal or reverse switch position for the associated track switch, initiating circuit means responsive to said manually operable switch designation for initiating said code communication apparatus into a cycle of operation for the transmission of the designated switch control, said initiating circuit means being effective only provided that said normal and reverse magnetic-stick switch indication relays for the associated track switch are both actuated to the same position.

10. A centralized trafiic control system for the control of a plurality of track switches and signals at a lield station by code communication from a distant control o'ice comprising in combination, normally at rest code communication apparatus connecting the control otice and the eld station and effective when initiated at the control oice to transmit selected control codes to the field station and effective when initiated at the eld station to transmit selected indication codes to the control oice, manually operable switch control designation means at the control oiice for designating respective switch control codes for transmission to the iield station, normal and reverse magnetic-stick indication relays at the control otice for the respective normal and reverse positions of the respective track switches, circuit means for energizing each of said magnetic-stick relays with one polarity in response to the designation by said manually operable means of the opposite position of the associated track switch, said circuit means being effective to energize each of said magnetic-stick relays with the opposite polarity in response to the communication by said code communication system of the corresponding normal or reverse position of the associated track switch, initiating circuit means responsive to said manually operable switch designation means for initiating said code communication apparatus into a cycle of operation for transmission of each designated switch control, said initiating circuit means being elective only provided that said normal and reverse magnetic-stick switch indication relays for the associated track switch are both actuated to the same positions, manually operable designation means at the control oice for designating respective signal control codes for transmission to the field station, and initiating circuit means responsive to said manually operable signal designation means for initiating said code communication apparatus into a cycle of operation for the transmission of the designated signal control code, said initiating circuit means for the transmission of signal control codes being effective only provided that one of said magnetic-stick relays is actuated in correspondence with the full-normal or full-reverse position of its associated track switch for each track switch included in a route emanating from the signal that has been designated.

References Cited in the tile of this patent UNTTED STATES PATENTS 2,211,522 Spray Aug. 13, 1940 2,211,523 Spray Aug. 13, 1940 2,223,126 Phinney Nov. 26, 1940 2,592,704 Jerome et al Apr. 15, 1952 

